DESCRIPTION: (Applicant's Description) On average, smokers weigh less than nonsmokers, and most smokers gain 2-3 kg of weight in the first six months of a cessation attempt. Fear of weight gain is a significant barrier to cessation attempts, particularly among women who smoke as a weight control strategy. For all its clinical relevance, little is known about the metabolic mechanisms of post-cessation weight gain or strategies to prevent it, esp. in women. This study will utilize a human indirect calorimetry chamber to assess exercise-related energy expenditure in 20 pre-menopausal women who are regular smokers. Each will participate in a pre-cessation assessment of resting energy expenditure, response to 20 minutes of standardized light exercise, and recovery time from exercise. The entire sample will then quit smoking for 72 hours, half using a 21 mg patch, half without nicotine replacement, and repeat the calorimetry assessment. The results should indicate the degree to which nicotine replacement therapy can increase exercise-related energy expenditure and/or prolong metabolic recovery time. Providing women with an active intervention to address weight gain may increase the number of successful cessation attempts, and may aid those who relapse due to fear of weight gain.